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Winter 2014-2015 Pattern Discussion Thread III


BIG FROSTY

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The 11-15 GFS continues to look nice with a combo of the return of W ridging and increased upper lat. blocking. By that time, models suggest that the MJO may be in the favorable phases near or within the COD. Keep in mind that climo for late Jan. sees an increase in major wintry precip. frequency. As a result of all of this, we may very well be finally seeing an exciting pattern starting within about the next two weeks. Keep watching the GEFS day 10 AO prog as it has had a high correlation to reality. The weak Niño -high end neutral pos./strong +PDO will hopefully finally start paying off with wintry in addition to strong cold. There's no need to dwell on negativity so relatively early in the active wintry part of the season IMO. The lack of sig wintry precip to this point outside of 11/1 has a low correlation to the prospects for sig wintry precip for the rest of winter. I'm sure Webber will agree with this. Climo definitely says this.

 

Oh I agree, once the climatological position of the Aleutian Low shifts southward in February, (the shift over the course of a +PDO winter is as I mentioned several days ago equivalent to having the MJO in the COD vs w/ amplitude in the Pacific.) the SE US ridge will thus get kicked further offshore & more than likely the core of the cold will shift southeastward as a result... Additionally, I mentioned on the mid-Atlantic blog that even if the AO remains positive again in January, it's not likely to stay that way into February. In fact, we've seen 9 +ENSO events since 1950 w/ a +AO in December & January (1951-52, 1972-73, 1982-83, 1990-91, 1991-92, 1992-93, 1994-95, 2004-05, & 2006-07), and of those years, only 4 (1972-73, 1991-92, 1992-93, 1994-95) also observed positively averaged AO in February, and not surprisingly all of these years fell within the cold phase of the AMO. Coincidence? I think not...

 

The global SST difference between the two subsets of years shows in advance of +ENSO winters that observe the AO finally flip its sign in Feb have comparatively warmer water in the extreme north Atlantic southeast of Atlantic Canada & Greenland, a SST distribution w/ similarities to the +AMO phase...

IRdjsp0raH.png

 

This year seems to be more analogous to those that flipped in February, however the cold horseshoe of water embedded within the Canary Current isn't characteristic of the +AMO, & the recent interdecadal rendition of the ENSO index is more than likely to blame for that. (i.e. a lack of El Ninos to positively spike the AMO)

NDJ-AMO-SST-Correlation.gif

Dec-28-Jan-5-2015-Global-SSTs.gif

The AMO essentially acts as a loading pattern for the NAO & AO, where in the cold phase of the AMO features rising NAO/AO tendency as the meridional SST gradient intensifies between the subtropics and the higher latitudes, thus strengthening the semi-permanent Icelandic Low, whereas the warm phase w/ +SST tripole, lowers the SST gradient, ( & thus geopotential height & temperature gradients) which cause the jet to slow down. This lowers its inertia & makes conditions generally more conducive meandering of the jet & hence high latitude blocking.

The NAO/AO as a result lag the AMO by half a phase cycle, w/ regime shifts in the AMO signaling a flip in the inter/multidecadal NAO/AO tendencies (i.e. warm AMO flipping to cold=upcoming/increasing +AO/NAO tendency, & vis versa). We should continue to remain in the increasing negative tendency w/ respect to both the AO/NAO indices until we observe a full blown flip in the AMO

JFM-Seasonal-AONAO-Index-AMO-Regime-Flip

 

On another note, the January Warm Neutral-Weak El Nino temperature composites have been spot on thus far in January, but unfortunately they may not continue to look this perfect before its all set & done. Regardless I couldn't be more pleased w/ how things are turning out temperature wise this month...

ncep_cfsr_noram_t2m_anom-1024x768.png

US-Winter-Monthly-Temps-DJF-El-Nino-Plac

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From the chart, it looks like we're, overall, in a strong-traditional El Nino, if I'm not mistaken.

 

December was a blend of the traditional-weak composites, closest analog being December 1939... (kudos to GaWx again for highlighting this analog at least several weeks in advance).

You could certainly make a viable argument for how the interdecadal ENSO trends we're currently observing is similar to the 1930s, (and the hurricane ACE trends are also following suit as one would expect, i.e. a sudden drop in hurricane ACE despite the favorable +AMO phase after coming off a record hurricane season several years earlier (1933, which still stands as the most active Atlantic Hurricane Season on record, even w/o satellite detection, it still outperformed 2005 by ~10pts)

 

Atlantic-Hurricane-ACE-1851-2013-1024x52

 

Link to the hurricane ACE record since 1851, along w/ Named Storm, Hurricane, & Major Hurricane counts.

http://www.aoml.noaa.gov/hrd/tcfaq/E11.html

 

This January is clearly behaving like a Warm Neutral-Weak/Modoki El Nino w/ the core of the cold down the center of the US & diffusion further east & residual warmth west of the Rockies. Going forward that's "amazing" is how the composites, no matter the intensity nor placement of the El Nino, all feature a southeastward shift in the core of the cold in February, that's a testament to the extent of the correspondence between Aleutian Low placement & sensible weather pattern. If this February doesn't end up being below normal, then something is clearly wrong. Historically, the probability of GA, SC, & NC ending up above normal in Feb in +ENSO irregardless of other conditions is low, close to 30%, while chances are actually 50% higher that the anomalies at least in either GA, SC, & NC end up at least 1 standard deviation below normal in February...

Top-20-PDOEl-Ninos-Weak-El-Nino-Warm-NeuGA-SC-NC-Monthly-Winter-Temperature-Stat

 

 

And that ^, is how you make a pattern thread post.

 

Thanks. I'd certainly hate to see a winter like this go to waste. Typically the biggest -AO/NAO winters tend to arrive right before the AMO flips into its cold phase, and we're definitely on the backside of this current warm cycle that's been ongoing since 1995.

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Check out the PARA dropping a 1046mb high down at 240 hours where on the 12z it was nowhere to be found...GFS is looking pretty stormy throughout entire run...

 

Qjcwbjb.png

 

 

Until we can start to get blocking cranked up over Greenland & the far North Atlantic, the most likely wintry wx threats (if any) will mainly stem from Miller B/CAD & overrunning events. High-latitude blocking over the Pacific (-WPO/EPO) tends to favor Miller B/CAD, while significant -AO/NAO regimes are more conducive to Miller As... 

NC-Miller-AMiller-B-WPO-EPO-AO-NAO1-1024

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Until we can start to get blocking cranked up over Greenland & the far North Atlantic, the most likely wintry wx threats (if any) will mainly stem from Miller B/CAD & overrunning events. High-latitude blocking over the Pacific (-WPO/EPO) tends to favor Miller B/CAD, while significant -AO/NAO regimes are more conducive to Miller As... 

 

 

I would also like to add that although a -EPO/WPO is certainly helpful in @ least delivering copious amounts of true, arctic air into the east-central US, the one caveat if you have a personal preference for Miller As & snowstorms is the confluent flow that is generated near the base of the subsequent trough that becomes established over the eastern US & southern Canada, which leads to episodic strong highs progressing thru the northern tier & southern Canada. If timed right w/ disturbances in the southern branch this = relatively high probability for ice instead of snow...

 

On another note, I find it very interesting how similar the January warm-neutral/weak El Nino 500mb & US temperature distribution looks to the correlated -EPO/WPO patterns. I think it says a lot about the evolution of these weaker +ENSO events...

EPO-WPO-Warm-NeutralWeak-El-Nino-January

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I would also like to add that although a -EPO/WPO is certainly helpful in @ least delivering copious amounts of true, arctic air into the east-central US, the one caveat if you have a personal preference for Miller As & snowstorms is the confluent flow that is generated near the base of the subsequent trough that becomes established over the eastern US & southern Canada, which leads to episodic strong highs progressing thru the northern tier & southern Canada. If timed right w/ disturbances in the southern branch this = relatively high probability for ice instead of snow...

On another note, I find it very interesting how similar the January warm-neutral/weak El Nino 500mb & US temperature distribution looks to the correlated -EPO/WPO patterns. I think it says a lot about the evolution of these weaker +ENSO events...

EPO-WPO-Warm-NeutralWeak-El-Nino-January

Really interesting stuff. Seems to be fitting our pattern to a T so far this January and if I recall correctly to an extent part of December (at least in regards to frequent cold air damning events) even though US temp averages did not match up.

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Folks,

Today's GEFS AO prog continues to progress in the negative direction. For the first time in over 3 weeks, the day 7 mean (for 1/18) has fallen back to 0. Keep in mind that it has had a very good score at day 7, an 85% correlation. Also, the bias at day 7 has been averaging +0.12. That means that the odds would actually favor it even going slightly negative by day 7. Looking at the chart, it could actually go slightly negative as early as day 5. After day 5-7, it looks like it may temporarily rise before heading back down. Day 14 continues with its negative prog at ~-1 though day 14 accuracy has been low. Accuracywise, a key is to get within day 10.

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao.sprd2.gif

The MJO has finally made it over to phase 6 as progged over the last couple of days after spending the 1st 8 days of the month in phase 5. Interestingly, KATL just had its coldest JAN phase 5 (amp. >1) day on record (going back to 1975) on 1/8/15. The model consensus now has it turning sharply left and making its way over to low amp phase 7 by 1/15 and then into low amp phase 8 (either just outside or within the COD) shortly thereafter. This MJO path has generally favored a colder regime overall for the SE US in January, especially once near or inside the COD in phases 7-8.

http://www.cpc.noaa.gov/products/precip/CWlink/MJO/CLIVAR/clivar_wh.shtml

So, at least when looking at these two indices, it is hard to not like the direction in which they're headed. We'll see if this all bodes well for later this month.

Looking at the 12Z GFS fwiw, it looks really nice with strong west coast ridging starting ~1/23 and persisting through the end of the run.

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Folks,

Today's GEFS AO prog continues to progress in the negative direction. For the first time in over 3 weeks, the day 7 mean (for 1/18) has fallen back to 0. Keep in mind that it has had a very good score at day 7, an 85% correlation. Also, the bias at day 7 has been averaging +0.12. That means that the odds would actually favor it even going slightly negative by day 7. Looking at the chart, it could actually go slightly negative as early as day 5. After day 5-7, it looks like it may temporarily rise before heading back down. Day 14 continues with its negative prog at ~-1 though day 14 accuracy has been low. Accuracywise, a key is to get within day 10.

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao.sprd2.gif

The MJO has finally made it over to phase 6 as progged over the last couple of days after spending the 1st 8 days of the month in phase 5. Interestingly, KATL just had its coldest JAN phase 5 (amp. >1) day on record (going back to 1975) on 1/8/15. The model consensus now has it turning sharply left and making its way over to low amp phase 7 by 1/15 and then into low amp phase 8 (either just outside or within the COD) shortly thereafter. This MJO path has generally favored a colder regime overall for the SE US in January, especially once near or inside the COD in phases 7-8.

http://www.cpc.noaa.gov/products/precip/CWlink/MJO/CLIVAR/clivar_wh.shtml

So, at least when looking at these two indices, it is hard to not like the direction in which they're headed. We'll see if this all bodes well for later this month.

Looking at the 12Z GFS fwiw, it looks really nice with strong west coast ridging starting ~1/23 and persisting through the end of the run.

I agree. The ensembles look great at the end of the run....can't help but not that look on both the GEFS and EPS mean. 00z Euro control builds a tall ridge and drops the PV on the 26th. Last week of Jan looking up, and Feb as well. I have a feeling the next weeklies are going to hint at a decent pattern headed into Feb.

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Here's why I'm optimistic. Despite being in its warmest January MJO phase, 5 outside of the circle and well outside of it at that, and there being a strong +AO (~+2.6) as well as strong +NAO (+1.8), Atlanta just had its coldest outside of the circle Jan phase 5 day on 1/8/15 by 3 F. JAN MJO records go back to 1975.

So, with a very noncooperative MJO, AO, and NAO, ATL still managed to have a very cold 1/8/15! And now all of these are headed in a better direction, especially the MJO and AO. Of course, any direction just about has to be better. But the MJO and AO are moving pretty abruptly in a better direction. Combine that with a weak Niño/high end neutral positive ENSO as well as a strong +PDO and it is hard not to be optimistic about late Jan into Feb, especially considering Webber's late season more favored climo for SE wintry wx and no matter how sucky wintry precip. has been to this point outside of those areas of SC that got hit on 11/1.

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That's an even bigger lol. Come on, folks. Past 240? Srsly.

Lol patterns have been picked up past 240 before. It's interesting because there's similarities in both model means when teleconnections are also progged to improve. There's no other way to see anything evolving if you don't look. ;) models in range to Feb should start (and are) spitting out interesting looks. Stop being so Widre today!
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